1. Field of the Invention
The present invention relates to lubricant for cold working for metallic conduits, and more particularly to a lubricant for cold working which is highly stable during its storage as well as during its use, excellent in lubricating performance, and also, readily removable after processing work.
2. Prior Art
For processing various types of metallic conduits, such as steel pipe, etc. with cold working (rolling, extrusion, stretching, etc.), various types of lubricants are used for the purpose of quality upgrading of processed products and of inhibitory control on the abrasion (prevention of burning) of the machine shop tools.
However, the commonly known lubricants are not necessarily equipped with all of the required characteristics such as high lubricating performance, readiness in removal after processing, and low polluting potential of the waste solution. For example, in relatively light working processes, plastic process oils, such as metallic soap and mineral oil, or a mixture of them, are used. However, in a process wherein high precision work is required, even when the above mentioned plastic process oils are employed, since the metal contact area between the pipes to be processed and the machine shop tools is large, damage to the tools and products is likely to increase. To cope with the foregoing problems, lubricants with lubricating resin content dissolved in an organic solvent was proposed. However, during use of such lubricant, the solvent becomes volatilized, making it difficult to control the concentration of the components. Further, health hazards due to the volatile solvent are likely to occur.
A relatively new method for lubrication forms a chemical conversion coating over the surface of metallic pipe material in advance to improve lubricating performance by chemical conversion metallic soap coating. This type of conversion coating includes phosphate coating (applied to common steel, low alloy steel, etc.), aluminum fluoride coating (applied to A1 or A1-base alloy), oxalate coating (applied to stainless steel, etc.) etc. In this method, a conversion coating is integrated between the pipe to be processed and the chemical converion metallic soap coating, and the foregoing pipe, conversion metallic soap coating and the conversion coating are chemically integrated, respectively. Therefore, the lubricating film shows markedly secure adhesiveness, and even when the rolling reduction (draft) is increased, sufficient lubricating performance is demonstrated.
However, the aforementioned lubricating method using chemcial conversion coating has the following problems:
a. Because the adhesiveness to the material to be processed is very high in degree, acid pickling is indispensable for removing the chemical conversion coating after completion of the processing.
b. Handling of the lubricant is complicated, and also the stability of the treatement effect is somewhat low.
c. A great deal of equipment and labor are required to clean-up the waste solution since a large quantity of waste solution results from the chemical treatment and acid pickling.
d. When the material used is highly corrosive, the chemical conversion treatment itself is difficult to apply and uniform chemical conversion coating cannot be formed. As a result, it is impossible to carry out high precision processing work.